1. Field of the Invention
The present invention relates to a microcomputer equipped with a built-in temperature sensor, which is capable of avoiding the occurrence of faulty operation and runaway of the microcomputer mounted on a semiconductor chip, even if the temperature of the semiconductor chip rises under the fluctuation of various conditions of circumstance during the operation of the microcomputer.
2. Description of the Related Art
In general, the entire electrical characteristic of a microcomputer is greatly changed under the fluctuation of the values of conductance and resistances of transistors incorporated in the microcomputer. This fluctuation is caused by the change of various conditions of circumstance, such as the operation temperature and the like, during the operation of the microcomputer.
When the temperature of the microcomputer rises during operation, the electrical characteristic thereof is shifted to a small operation margin. When the electrical characteristic is reached to and over the boundary of the operation margin, the runaway of the microcomputer occurs.
In order to avoid the occurrence of the runaway of the microcomputer, it must be necessary to compensate the operation of the microcomputer under the fluctuation of various conditions of circumstance during operation. In order to achieve this requirement, a simulation is performed in the design of the microcomputer under a temperature range. This temperature range is predicted under the various conditions of circumstance during operation.
However, it is difficult to get the optimum temperature range in the conditions of circumstance as actual operation under the state in which the microcomputer is incorporated in actual commercial products. Further, there is a drawback where different regions in the same semiconductor chip on which the microcomputer is mounted have difference temperatures.
Because the conventional microcomputer has the above configuration and the drawbacks, the simulation is executed under a wider and waste temperature range. However, in use of the microcomputer, there happens a case where the temperature of the microcomputer during operation becomes over the temperature range that has been predicted in the design. As a result, the runaway of the microcomputer occurs, so that the faulty operation of the microcomputer also happens.
Accordingly, an object of the present invention is, with due consideration to the drawbacks of the conventional technique, to provide a microcomputer equipped with a built-in temperature sensor, which is mounted on a semiconductor chip, capable of avoiding the occurrence of faulty operation and runaway, even if the temperature of the semiconductor chip rises over a prescribed value by fluctuation of various conditions of circumstance during the operation of the microcomputer. The temperature sensor or both the temperature sensor and a voltage break circuit are incorporated in the microcomputer the voltage break circuit is operable under a predetermined temperature range. The temperature sensor is capable of detecting an inner temperature of the semiconductor chip in order to set the optimum operation conditions of the microcomputer.
In accordance with a preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has diodes incorporated in a pair of circuit blocks, the diodes being placed in opposite polarity connection to each other, a first terminal group connected commonly to the each diode, through which a constant current is supplied, and a second terminal group through which a voltage generated at each diode is read, and connected commonly to and placed at more adjacent nodes to the each diode when compared with the first terminal group. Thereby, optimum operation conditions of the microcomputer can be set according to the change of the temperature of the microcomputer.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a diode incorporated in each of a plurality of circuit blocks, a first terminal group connected commonly to the each of the plurality of diodes, through which a constant current is supplied, a second terminal group through which a voltage generated at each of the plurality of diodes is read, and connected commonly to and placed at more adjacent nodes to the each of the plurality of diodes when compared with the first terminal group, a selection switch for selecting one of the plurality of diodes, and a selection register in which a prescribed value to control operation of the selection switch is stored. Thereby, optimum operation conditions of the microcomputer can be set according to the change of the temperature of the microcomputer.
In the microcomputer equipped with a built-in temperature sensor described above, the plurality of circuit blocks are divided into plural pairs, each pair consists of two circuit blocks. The diodes incorporated in each pair are placed in opposite polarity connection to each other, and the selection switch selects one pair of the two circuit blocks in the plurality of circuit blocks according to the prescribed value stored in the selection register. Thereby, optimum operation conditions of the microcomputer can be set according to change of the temperature of the semiconductor chip.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a temperature sensor circuit having a diode and a first resistance connected in series between a first power source voltage and a second power voltage source, a MOS inverter circuit, and a terminal connected to a second node through which the second resistance and the first MOS transistor are connected. The MOS inverter circuit has a first MOS transistor whose gate is connected to a node through which the diode and the first resistance being connected, and a second resistance connected to the first MOS transistor in series. In the microcomputer, the second resistance is connected to the first power source voltage, and the first MOS transistor is connected to the second power source voltage, and the temperature sensor circuit and the MOS inverter circuit forms a voltage break circuit.
In the microcomputer equipped with a built-in temperature sensor described above, a plurality of the MOS inverter circuits are placed in parallel. Each MOS inverter circuit has the first MOS transistor and the second resistance. Threshold values of the first MOS transistors in the plurality of MOS inverter circuits are set stepwise. The gates of the first MOS transistors are commonly connected to the first node, and each of the second nodes of the plurality of MOS inverter circuits is connected to, instead of the terminal, a corresponding register in which a value corresponding to a voltage potential at each second node.
The microcomputer equipped with a built-in temperature sensor, as another preferred embodiment of the present invention, further has a selection switch for selecting one of the plurality of MOS inverter circuits in order to connect the selected MOS inverter to the temperature sensor circuit and the terminal through the first node and the second node, and a selection register for storing a prescribed value by which an operation of the selection switch is controlled.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a temperature monitor circuit for generating and outputting a control signal when a temperature of a semiconductor chip on which the microcomputer is mounted rises over a prescribed value, an interrupt circuit for inputting the control signal output from the interrupt circuit to initiate an interrupt operation, a CPU core for halting temporarily generation of a clock signal according to an instruction output from the interrupt circuit, and a timer circuit. The timer circuit initiates a counting operation according to the instruction to initiate the interrupt operation which is output from the interrupt circuit, and generates an instruction to restart the generation of the clock signal to the CPU core after a counted number obtained by the counting operation reaches to a predetermined number.
In the microcomputer equipped with a built-in temperature sensor, as another preferred embodiment of the present invention, the temperature monitor circuit has a temperature sensor circuit having a diode and a first resistance connected in series between a first power source voltage and a second power voltage source, a plurality of MOS inverter circuits, a NOR circuit connected to each second node through which the first MOS transistor and the second resistance in each of the plurality of MOS inverter circuits are connected, and a temperature selection register for storing prescribed values to be used for controlling ON/OFF operation of each second MOS transistor. The temperature selection register is connected to a gate of the second MOS transistor in each of the plurality of MOS inverter circuits. The NOR circuit performs a NOR operation between values of the second nodes. Each MOS inverter circuit has a first MOS transistor whose gate is connected to a first node through which the diode and the first resistance are connected, and a second resistance and a second MOS transistor which are connected in series and placed to the first MOS transistor.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, the temperature monitor circuit has a temperature sensor circuit (which has a diode and a first resistance connected in series between a first power source voltage and a second power voltage source), an A/D converter for converting an analogue voltage value at a first node between the diode and the first resistance to a digital voltage value, a temperature monitor register for storing the digital voltage value output from the A/D converter, a prescribed value register for storing a prescribed value, and a comparator for comparing the digital voltage value in the temperature monitor register with the prescribed value stored in the prescribed value, and for outputting a comparison result as a control signal.
The microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, further has a plurality of the temperature monitor circuits, and a NOR circuit for inputting control signals which are output from the plurality of the temperature monitor circuits, for performing a NOR operation among the control signals, and for outputting a result of the NOR operation to the interrupt circuit.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a temperature monitor circuit, a CPU core, an interrupt circuit, and a timer circuit. The temperature monitor circuit generates and outputs a control signal when a temperature of a semiconductor chip on which the microcomputer is mounted rises over a prescribed value. The CPU core has a control register, inputs the control signal from the temperature sensor circuit and storing the control signal. The interrupt circuit initiates an interrupt operation to halt a generation operation of a clock signal executed by the CPU core according to the control signal stored in the control register. The timer circuit initiates a counting operation according to the control signal stored in the control register, and generates an instruction to restart the generation operation of the clock signal to the CPU core after a counted number obtained by the counting operation reaches to a predetermined number.
The microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, further has a plurality of the temperature monitor circuits, and a NOR circuit. The NOR circuit inputs control signals which are output from the plurality of the temperature monitor circuits, performs a NOR operation among the control signals, and outputs a result of the NOR operation to the CPU core.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, the temperature monitor circuit has a temperature sensor circuit, a NOR circuit, and a temperature selection register. The temperature sensor circuit has a diode and a first resistance connected in series between a first power source voltage and a second power voltage source, a plurality of MOS inverter circuits. Each MOS inverter circuit has a first MOS transistor whose gate is connected to a first node through which the diode and the first resistance are connected, and a second resistance and a second MOS transistor which are connected in series and placed to the first MOS transistor. The NOR circuit is connected to each second node through which the first MOS transistor and the second resistance in each of the plurality of MOS inverter circuits are connected. The NOR circuit performs a NOR operation between values of the second nodes. The temperature selection register is connected to a gate of the second MOS transistor in each of the plurality of MOS inverter circuits. The temperature selection register stores prescribed values to be used for controlling ON/OFF operation of each second MOS transistor.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, the temperature monitor circuit has a temperature sensor circuit, an A/D converter, a temperature monitor register, a prescribed value register, and a comparator. The temperature sensor circuit has a diode and a first resistance connected in series between a first power source voltage and a second power voltage source. The A/D converter converts an analogue voltage value at a node between the diode and the first resistance to a digital voltage value. The temperature monitor register stores the digital voltage value output from the A/D converter. The prescribed value register stores a prescribed value. The comparator compares the digital voltage value in the temperature monitor register and the prescribed value stored in the prescribed value, and outputs a comparison result as a control signal.
The microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, further has a plurality of the temperature monitor circuits, and a NOR circuit for inputting control signals which are output from the plurality of the temperature monitor circuits, for performing a NOR operation among the control signals, and for outputting a result of the NOR operation to the control register in the CPU core. In the microcomputer, the interrupt circuit outputs an instruction to initiate the interrupt operation to the CPU core according to a value of the control signal which is stored in the control register, and for outputting an instruction to initiate the counting operation to the timer circuit simultaneously.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a voltage break circuit and a power source voltage generation circuit. The voltage break circuit has a temperature sensor circuit placed in a circuit block (which has a diode and a first resistance connected in series to a first power source voltage and a second power source voltage), a first MOS transistor whose gate is connected to a first node through which the diode and the first resistance are connected, and a second resistance connected in series to the first MOS transistor. In the voltage break circuit, the second resistance is connected to the first power source voltage, and the first MOS transistor is connected to the second power source voltage. The power source voltage generation circuit in which a selector is incorporated, the selector inputs a control voltage signal output from the voltage break circuit, and selects one of a first voltage and a second voltage based on a level of the control voltage signal, and outputs the voltage.
The microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, further has a plurality of the MOS inverter circuits, a selection switch, and a selection register. The plurality of the MOS inverter circuits are placed in parallel, each MOS inverter circuit has the first MOS transistor and the second resistance, and threshold values of the first MOS transistors in the plurality of MOS inverter circuits are set stepwise. The selection switch selects one of the plurality of MOS inverter circuits and connects the selected one to the temperature sensor circuit and the power source voltage generation circuit. The selection register stores a prescribed value by which operation of the selection switch is controlled.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a temperature sensor circuit, an A/D converter, a temperature monitor register, a prescribed value register, a comparator, and a power source voltage generation circuit. The temperature sensor circuit has a diode and a first resistance connected in series between a first power source voltage and a second power voltage source. The A/D converter converts an analogue voltage value at a first node through which the diode and the first resistance to a digital voltage value. The temperature monitor register stores the digital voltage value output from the A/D converter. The prescribed value register stores a prescribed value. The comparator compares the digital voltage value in the temperature monitor register and the prescribed value stored in the prescribed value register, and outputs a comparison result. The power source voltage generation circuit has a selector. The selector selects one of a first voltage and a second voltage based on a level of the comparison result, and outputs the selected voltage.
The microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, further has a plurality of the prescribed value registers for storing a plurality of prescribed values, and a plurality of the comparators corresponding to the plurality of prescribed value registers. In the microcomputer, each of the plurality of comparators inputs an output from the temperature monitor register and the prescribed value from the corresponding prescribed value register.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a voltage break circuit, and a wait control circuit. The voltage break circuit has a temperature sensor circuit incorporated in a circuit block (having a diode and a first resistance connected in series to a first-power source voltage and a second power source voltage), a MOS transistor whose gate is connected to a first node through which the diode and the first resistance are connected, and a second resistance connected in series to the MOS transistor. In the voltage break circuit, the second resistance is connected to the first power source voltage, and the MOS transistor is connected to the second power source voltage. The wait control circuit having a selector. The selector inputs a control voltage signal output from the voltage break circuit, and selects one of a first clock signal of a first cycle and a second clock signal of a second cycle based on a level of the control voltage signal, and outputs the selected clock signal in order to adjust an accessing time by which an external device is accessed correctly.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, a circuit is incorporated instead of the voltage break circuit, the circuit has a temperature sensor circuit comprises a diode and a first resistance connected in series between a first power source voltage and a second power voltage source, an A/D converter for converting an analogue voltage value at a first node through which the diode and the first resistance to a digital voltage value, a temperature monitor register for storing the digital voltage value output from the A/D converter, a prescribed value register for storing a prescribed value, and a comparator for comparing the digital voltage value in the temperature monitor register and the prescribed value stored in the prescribed value register, and for outputting a comparison result. In the microcomputer, the selector incorporated in the wait control circuit selects one of the first clock signal of a first bus cycle and the second clock signal of a second bus cycle based on the comparison result from the comparator.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, a first output buffer, a second output buffer, and a switch are incorporated instead of the wait control circuit. In the microcomputer, the switch inputs the control voltage signal output from the voltage break circuit, and selects one of or both the first output buffer and the second output buffer based on a level of the control voltage signal.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, a first output buffer, a second output buffer, and a switch are incorporated instead of the wait control circuit. In the microcomputer, the switch inputs the comparison result output from the comparator, and selects one of or both the first output buffer and the second output buffer based on a level of the comparison result.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, a high temperature mode bit circuit is incorporated instead of the wait control circuit. The high temperature mode bit circuit inputs the control voltage signal output from the voltage break circuit, and switches operation modes of the microcomputer, a high temperature operation mode and a normal operation mode, according to a level of the control voltage signal.
In the microcomputer equipped with a built-in temperature sensor described above, as another preferred embodiment, a high temperature mode bit circuit is incorporated instead of the wait control circuit. This high temperature mode bit circuit inputs the comparison result output from the comparator, and switches operation modes of the microcomputer, a high temperature operation mode and a normal operation mode, according to a level of the comparison result.